In recent years, as power storage means for storing a large capacity of power, a power storage module in which a plurality of power storage cells are connected to each other has been used. For example, a battery module in which hundreds of lithium ion battery cells are connected in series to each other is mounted in an electric vehicle (EV) or a hybrid electric vehicle (HEV), and the battery module generates a voltage of hundreds of V so as to drive a motor.
In a power storage module, it is important to understand a state of charge (SOC) or a state of health (SOH) of a power storage cell with high accuracy. For example, in a case of an on-vehicle application, an SOC is understood with high accuracy, a cruising range of a vehicle can be increased by reducing a margin of residual quantity computation error for a charge amount, or mileage can be improved by reducing a battery weight through reduction of the number of serial connections or parallel connections of power storage cells mounted for a margin of error.
In order to understand an SOC or an SOH of power storage cells with high accuracy, it is preferable to measure voltages of a plurality of power storage cells and a current flowing therethrough at the same timing with high accuracy.
PTL 1 discloses a configuration of detecting a voltage of a battery module forming a battery for traveling as a vehicular power source device. In this configuration, battery cells of the battery module are sequentially selected by using a multiplexer, and a voltage value of a selected battery cell is measured by using an analog-to-digital converter (ADC).